1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to an electrode structure of a plasma display panel that is capable of improving the brightness. Also, the present invention is directed to a method of driving a sustaining electrode in the plasma display panel.
2. Description of the Related Art
Generally, a plasma display panel (PDP) is a light-emitting device which displays a picture using a gas discharge phenomenon within the cell. This PDP does not require providing an active device for each cell like a liquid crystal display (LCD). Accordingly, the PDP has a simple fabrication process and has the advantage of providing a large-dimension screen.
Such a PDP has a number of discharge cells arranged in a matrix type. The discharge cells are provided at each intersection between sustaining electrode lines for sustaining a discharge and address electrode lines for selecting the cells to be discharged. The PDP is largely classified into a direct current (DC) type panel and an alternating current (AC) type panel depending on whether or not a dielectric layer for accumulating a wall charge exists in the discharge cell.
Referring to FIG. 1 and FIG. 2, each cell of the AC-type, three-electrode PDP includes a front substrate 11 provided with a sustaining electrode pair 12A and 12B, and a rear substrate 18 provided with an address electrode 20. The front substrate 10 and the rear substrate 18 are spaced in parallel to each other with having barrier ribs 24 therebetween and sealed with a fritz glass. A mixture gas, such as Nexe2x80x94Xe or Hexe2x80x94Xe, etc., is injected into a discharge space defined by the front substrate 11, the rear substrate 18 and the barrier ribs 24. The sustaining electrode pair 12A and 12B makes a pair by two within a single of plasma discharge channel. Any one electrode of the sustaining electrode pair 12A and 12B is used as a scanning electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode 20 while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge along with the other adjacent sustaining electrode. Also, the sustaining electrode 12B or 12A adjacent to the sustaining electrode 12A or 12B used as the scanning electrode is used as a common sustaining electrode to which a sustaining pulse is applied commonly.
The sustaining electrode pair 12A and 12B includes transparent electrodes 30A and 30B and metal electrodes 28A and 28B connected electrically to each other, respectively. The transparent electrodes 30A and 30B is formed by depositing indium thin oxide (ITO) on the front substrate 10 into an electrode width of about 300 m so as to prevent deterioration of an aperture ratio. The metal electrodes 28A and 28B are deposited on the front substrate 10 to have a three-layer structure of Ag or Crxe2x80x94Cuxe2x80x94Cr. The metal electrodes 28A and 28B play a role to reduce a voltage drop caused by the transparent electrodes 30A and 30B.
On the front substrate 10 provided with the sustaining electrodes 12A and 12B, a dielectric layer 14 and a protective layer 16 are disposed. The dielectric layer 14 is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film 16 prevents a damage of the dielectric layer 14 caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 16 is usually made from MgO. The rear substrate 18 is provided with a dielectric thick film 26 covering the address electrode 24. The barrier ribs 24 for dividing the discharge space are extended perpendicularly at the rear substrate 18. On the surfaces of the rear substrate 18 and the barrier ribs 24, a fluorescent material 22 excited by a vacuum ultraviolet lay to generate a visible light is provided.
As shown in FIG. 3, such cells 1 of the PDP are arranged on a panel 30 in a matrix type. In each cell 1, scanning/sustaining electrode lines S1 to Sm, common sustaining electrode lines C1 to Cm and address electrode lines D1 to Dn cross each other. The scanning/sustaining electrode lines S1 to Sm and the common sustaining electrodes C1 to Cm consists of the sustaining electrode pair 12A and 12B in FIG. 1, respectively. The address electrode lines D1 to Dn consist of the address electrodes 20.
In such an AC-type PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields. Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. The cells on which a data is to be displayed are selected by a writing discharge in the address interval. The selected cells sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2n depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eighth sub-fields increases at a ratio of 20, 21, 23, 24, 25, 26 and 27. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 20, 21, 23, 24, 25, 26 and 27 depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields.
An emission process of the PDP will be described below. First, a wall charge is uniformly accumulated within the cells of the entire screen by the reset discharge generated in the reset interval. In the address interval, a writing discharge is generated at the cells selected by an address discharge voltage applied to the scanning/sustaining electrode lines S1 to Sm and the address electrode lines D1 to Dn. Subsequently, when a sustaining pulse is alternately applied to the scanning/sustaining electrode lines S1 to Sm and the common sustaining electrode lines C1 to Cm, a discharge of the cells selected in the address interval is sustained.
When a plasma discharge is generated within the cell, a very small amount of electrons in discharge gases within the cell begin to be accelerated and continuously collide with neutral particles. By such an avalanche effect, the discharge gases within the cell is rapidly ionized into electrons and ions to be in a plasma state and, at the same time, generate a vacuum ultraviolet. This vacuum violet excites the fluorescent material 22 to generate a visible light.
However, the conventional PDP has a limit in improving the brightness into a satisfying level in view of its discharge structure. More specifically, the sustaining discharge of the PDP begins at one opposite surface between the scanning/sustaining electrode lines S1 to Sm and the common sustaining electrode lines C1 to Cm and is gradually diffused all over the cells. In such a discharge structure, since the discharge concentrates on only one surface between the scanning/sustaining electrode lines S1 to Sm and the common sustaining electrodes C1 to Cm, the brightness becomes low.
Accordingly, it is an object of the present invention to provide an electrode structure of a plasma display panel and a method of driving a sustaining electrode in the plasma display panel that are adaptive for improving the brightness.
In order to achieve these and other objects of the invention, an electrode structure of a plasma display panel according to one aspect of the present invention includes refractive electrodes connected to a sustaining electrode pair and bent to generate a sustaining discharge at at least two positions within a cell.
A method of driving sustaining electrodes in a plasma display panel according to another aspect of the present invention includes the steps of forming refractive electrodes at the sustaining electrode pair to generate a sustaining discharge at at least two positions within the cell.